Network Working Group A. Doria (co-editor)
Internet-Draft ForCES Protocol Design Team
Expires: November 30, 2004 June 2004
ForCES Protocol Specificationdraft-doria-forces-protocol-01.txt
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Abstract
This is the first draft of the ForCES protocol specification produced
by the protocol design team. It is presented to the WG for
consideration as a WG work item.
Authors
The participants in the ForCES Protocol Team, authors and co-editors,
of this draft, are:
Ligang Dong, Zhejiang Gongshang University
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Internet-Draft ForCES June 20041. Introduction
The protocol defined in this ID is the first draft of the effort
being made by the ForCES Protocol Design team to develop a ForCES
protocol that meets the requirements set out in [RFC3654].
The team was created by the WG chairs of the ForCES group in
consultation with the Routing Area ADs after the authors of the
various qualifying drafts, i.e. drafts submitted by the deadline
which met the essential requirements outline in [RFC3654], reached
consensus on being able to develop a common protocol proposal.
While this draft has rough consensus within the design team, there
are still issues that need to be resolved. These issues will
continue to be discussed within the protocol design team and
hopefully, on the general ForCES WG email list.
The protocol design team was defined by the WG chairs to be composed
of seven participants includes two representatives from each of the 3
protocol proposals and 1 participant who had not contributed to the
proposed protocols.
The ForCES protocol defined in this draft is being presented to the
ForCES WG for consideration as a WG item corresponding to the charter
item:
Specification of IP-based protocol for transport of the controlled
objects. When the control and forwarding devices are separated
beyond a single hop, ForCES will make use of an existing RFC2914
compliant L4 protocol with adequate reliability, security and
congestion control (e.g. TCP, SCTP) for transport purposes.
1.1 Sections of this documentSection 2 provides a glossary of terminology used in the
specification.
Section 3 provides an overview of the protocol including a discussion
on the protocol framework, descriptions of the protocol layer (PL)
and a transport mapping layer (TML), as well as of the ForCES
protocol mechanisms.
While this document does not define the TML, Section 4 details the
services that the TML must provide.
The Forces protocol is defined to have a common header for all other
message types. The header is defined in Section 5, while the
protocol messages are defined in Section 6.
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Internet-Draft ForCES June 2004Section 8 describes mechanism in the protocol to support high
availability mechanisms including redundancy and fail over. Section9 defines the security mechanisms provided by the PL and TML.
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Internet-Draft ForCES June 20042. Definitions
This document follows the terminologies defined by the ForCES
Requirements in [RFC3654] and by the ForCES framework in [RFC3746].
This document also uses the terminologies defined by ForCES FE model
in [FE-MODEL]. We copy the definitions of some terminologies as
below:
Addressable Entity (AE) - A physical device that is directly
addressable given some interconnect technology. For example, on IP
networks, it is a device to which we can communicate using an IP
address; and on a switch fabric, it is a device to which we can
communicate using a switch fabric port number.
Forwarding Element (FE) - A logical entity that implements the ForCES
protocol. FEs use the underlying hardware to provide per-packet
processing and handling as directed/controlled by a CE via the ForCES
protocol.
Control Element (CE) - A logical entity that implements the ForCES
protocol and uses it to instruct one or more FEs how to process
packets. CEs handle functionality such as the execution of control
and signaling protocols.
Pre-association Phase - The period of time during which a FE Manager
(see below) and a CE Manager (see below) are determining which FE and
CE should be part of the same network element.
Post-association Phase - The period of time during which a FE does
know which CE is to control it and vice versa, including the time
during which the CE and FE are establishing communication with one
another.
FE Model - A model that describes the logical processing functions
of a FE.
FE Manager (FEM) - A logical entity that operates in the
pre-association phase and is responsible for determining to which
CE(s) a FE should communicate. This process is called CE discovery
and may involve the FE manager learning the capabilities of available
CEs. A FE manager may use anything from a static configuration to a
pre-association phase protocol (see below) to determine which CE(s)
to use. Being a logical entity, a FE manager might be physically
combined with any of the other logical entities such as FEs.
CE Manager (CEM) - A logical entity that operates in the
pre-association phase and is responsible for determining to which
FE(s) a CE should communicate. This process is called FE discovery
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and may involve the CE manager learning the capabilities of available
FEs. A CE manager may use anything from a static configuration to a
pre-association phase protocol (see below) to determine which FE to
use. Being a logical entity, a CE manager might be physically
combined with any of the other logical entities such as CEs.
ForCES Network Element (NE) - An entity composed of one or more CEs
and one or more FEs. To entities outside a NE, the NE represents a
single point of management. Similarly, a NE usually hides its
internal organization from external entities.
High Touch Capability - This term will be used to apply to the
capabilities found in some forwarders to take action on the contents
or headers of a packet based on content other than what is found in
the IP header. Examples of these capabilities include NAT-PT,
firewall, and L7 content recognition.
Datapath -- A conceptual path taken by packets within the forwarding
plane inside an FE.
LFB (Logical Function Block) type -- A template representing a
fine-grained, logically separable and well-defined packet processing
operation in the datapath. LFB types are the basic building blocks
of the FE model.
LFB (Logical Function Block) Instance -- As a packet flows through an
FE along a datapath, it flows through one or multiple LFB instances,
with each implementing an instance of a certain LFB type. There may
be multiple instances of the same LFB in an FE's datapath. Note that
we often refer to LFBs without distinguishing between LFB type and
LFB instance when we believe the implied reference is obvious for the
given context.
LFB Metadata -- Metadata is used to communicate per-packet state from
one LFB to another, but is not sent across the network. The FE model
defines how such metadata is identified, produced and consumed by the
LFBs, but not how metadata is encoded within an implementation.
LFB Attribute -- Operational parameters of the LFBs that must be
visible to the CEs are conceptualized in the FE model as the LFB
attributes. The LFB attributes include, for example, flags, single
parameter arguments, complex arguments, and tables that the CE can
read or/and write via the ForCES protocol (see below).
LFB Topology -- Representation of how the LFB instances are logically
interconnected and placed along the datapath within one FE.
Sometimes it is also called intra-FE topology, to be distinguished
from inter-FE topology.
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FE Topology -- A representation of how the multiple FEs within a
single NE are interconnected. Sometimes this is called inter-FE
topology, to be distinguished from intra-FE topology (i.e., LFB
topology).
Inter-FE Topology -- See FE Topology.
Intra-FE Topology -- See LFB Topology.
Following terminologies are defined by this document:
ForCES Protocol - While there may be multiple protocols used within
the overall ForCES architecture, the term "ForCES protocol" refers
only to the protocol used at the Fp reference point in the ForCES
Framework in RFC3746 [RFC3746]. This protocol does not apply to
CE-to-CE communication, FE-to-FE communication, or to communication
between FE and CE managers. Basically, the ForCES protocol works in
a master-slave mode in which FEs are slaves and CEs are masters.
This document defines the specifications for this ForCES protocol.
ForCES Protocol Layer (ForCES PL) -- A layer in ForCES protocol
architecture that defines the ForCES protocol messages, the protocol
state transfer scheme, as well as the ForCES protocol architecture
itself (including requirements of ForCES TML (see below)).
Specifications of ForCES PL are defined by this document.
ForCES Protocol Transport Mapping Layer (ForCES TML) -- A layer in
ForCES protocol architecture that specifically addresses the protocol
message transportation issues, such as how the protocol messages are
mapped to different transport media (like TCP, IP, ATM, Ethernet,
etc), and how to achieve and implement reliability, multicast,
ordering, etc. The ForCES TML is specifically addressed in a
separate ForCES TML Specification document.
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This is depicted in Figure 3 below.
+------------------------------------------------
| CE PL layer |
+------------------------------------------------
| CE TML layer |
+------------------------------------------------
^
|
ForCES | (i.e Forces data + control
PL | packets )
messages |
over |
specific |
TML |
encaps |
and |
transport |
|
v
+------------------------------------------------
| FE TML layer |
+------------------------------------------------
| FE PL layer |
+------------------------------------------------
Figure 3: ForCES Interface
The PL layer is in fact the ForCES protocol. Its semantics and
message layout are defined in this document. The TML Layer is
necessary to connect two ForCES PL layers as shown in Figure 3 above.
The TML is out of scope for this document but is within scope of
ForCES. This document defines requirements the PL needs the TML to
meet.
Both the PL and TML layers are standardized by the IETF. While only
one PL layer is defined, different TMLs are expected to be
standardized. To interoperate the TML layer at the CE and FE are
expected to be of the same definition.
On transmit, the PL layer delivers its messages to the TML layer.
The TML layer delivers the message to the destination TML layer(s).
On receive, the TML delivers the message to its destination PL
layer(s).
3.1.1 The PL layer
The PL is common to all implementations of ForCES and is standardized
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by the IETF as defined in this document. The PL layer is responsible
for associating an FE or CE to an NE. It is also responsible for
tearing down such associations. An FE uses the PL layer to throw
various subscribed-to events to the CE PL layer as well as respond to
various status requests issued from the CE PL. The CE configures
both the FE and associated LFBs attributes using the PL layer. In
addition the CE may send various requests to the FE to activate or
deactivate it, reconfigure its HA parametrization, subscribe to
specific events etc. More details in section Section 6.
3.1.2 The TML layer
The TML layer is essentially responsible for transport of the PL
layer messages. The TML is where the issues of how to achieve
transport level reliability, congestion control, multicast, ordering,
etc are handled. It is expected more than one TML will be
standardized. The different TMLs each could implement things
differently based on capabilities of underlying media and transport.
However, since each TML is standardized, interoperability is
guaranteed as long as both endpoints support the same TML. All
ForCES Protocol Layer implementations should be portable across all
TMLs, because all TMLs have the same top edge semantics as defined in
this document.
3.1.3 The FEM/CEM Interface
The FEM and CEM components, although valuable in the setup and
configurations of both the PL and TML layers, are out of scope of the
ForCES protocol. The best way to think of them are as
configurations/parameterizations for the PL and TML before they
become active (or even at runtime based on implementation). In the
simplest case, the FE or CE read a static configuration file which
they use as the FEM/CEM interface. RFC 3746 has a lot more detailed
descriptions on how the FEM and CEM could be used. We discuss the
pre-association phase where the CEM and FEM play briefly in section
Section 3.2.1.
An example of typical things FEM/CEM would configure would be TML
specific parameterizations such as:
a. how the TML connection should happen (example what IP addresses
to use, transport modes etc);
b. the ID for the FE or CE would also be issued at this point.
c. Security parameterization such as keys etc.
d. Connection association parameters
Example "send up to 3 association messages each 1 second apart" Vs "
send up to 4 association messages with increasing exponential
timeout".
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Internet-Draft ForCES June 20043.2 ForCES Protocol Phases
ForCES in relation to NEs involves two phases: the Pre-Association
phase where configuration/initialization/bootup of the TML and PL
layer happens, and the association phase where the ForCES protocol
operates.
3.2.1 Pre-association
The ForCES interface is configured during the Pre association phase.
In a simple setup, the configuration is static and is read from some
saved config file. All the parameters for the association phase are
well known after the pre association phase is complete. A protocol
such as DHCP may be used to retrieve the config parameters instead of
reading from a static config file. Note this will still be
considered static pre-association. Dynamic configuration may also
happen in the Fc, Ff and Fl reference points. Vendors may use their
own proprietary service discovery protocol to pass the parameters.
We reproduce some scenarios from the Framework Document to show a
pre-association example.
<----Ff ref pt---> <--Fc ref pt------->
FE Manager FE CE Manager CE
| | | |
| | | |
(security exchange) (security exchange)
1|<------------>| authentication 1|<----------->|authentication
| | | |
(FE ID, attributes) (CE ID, attributes)
2|<-------------| request 2|<------------|request
| | | |
3|------------->| response 3|------------>|response
(corresponding CE ID) (corresponding FE ID)
| | | |
| | | |
Figure 4: Examples of a message exchange over the Ff and Fc reference
points
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<-----------Fl ref pt--------------> |
FE Manager FE CE Manager CE
| | | |
| | | |
(security exchange) | |
1|<------------------------------>| |
| | | |
(a list of CEs and their attributes) |
2|<-------------------------------| |
| | | |
(a list of FEs and their attributes) |
3|------------------------------->| |
| | | |
| | | |
Figure 5: An example of a message exchange over the Fl reference
point
Before the transition to the association phase, the FEM will have
established contact with the appropriate CEM component.
Initialization of the ForCES interface will be completed, and
Authentication and capabilities discovery may be complete as well.
Both the FE and CE would know how to connect to each other for
configuration, accounting, identification and authentication
purposes. Both sides are also knowledgeable of all necessary
protocol parameters such as timers, etc. The Fl reference point may
continue to operate during the association phase and may be used to
force a disassociation of an FE or CE. Because the Pre-association
phase is out of scope, we do not discuss these details any further.
The reader is referred to the framework document for more detailed
discussion.
3.2.2 Post-association
In this phase, the FE and CE components talk to each other using the
ForCES protocol (PL over TML) as defined in this document. There are
three sub-phases: Association setup state, Established State, and
Association teardown state.
3.2.2.1 Association setup state
The FE attempts to join the NE. The FE may be rejected or accepted.
Once granted access into the NE, capabilities exchange happen with
the CE querying the FE. Armed with the FE capability knowledge, the
CE can offer an initial configure (possibly to restore state) and
query certain attributes within either an LFB or the FE itself.
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A lot more details are provided in the protocol scenarios section.
On successful completion of this state, the FE joins the NE and is
moved to the Established State.
3.2.2.2 Association Established state
In this state the FE is continuously updated or queried. The FE may
also send asynchronous event notifications to the CE or synchronous
heartbeat notifications. This continues until a termination is
initiated by either the CE or FE.
Refer to section on protocol scenarios for more details.
3.3 Protocol Mechanisms
Various semantics are exposed to the protocol users via the PL header
including: Transaction capabilities, atomicity of transactions, two
phase commits, batching/parallelization, High Availability and
failover as well as command windows.
3.3.1 Of Transactions, Atomicity and 2 Phase Commits
A transaction is a sequence of operations that is guaranteed to be
atomic in the presence of any failures by the CEs or FEs. Operation
in this sense implies the PL operation within the message body TLV.
An example of a transaction could be a config PL msg with a sequence
of operations: "route-add A B,C:route-del X" (each operation in its
own TLV).
If a transaction is split across more than one message, then all
message batch must arrive at the destination before they are executed
on either the LFB or FE. All operations are executed serially in the
order specified by the transaction. If any of the sequence of
operations in a transaction fails then the transaction is declared as
a failure. This is an all-or-nothing approach and is needed to
ensure consistency of a transaction across multiple FEs.
A transaction may be atomic within an FE alone or across the NE. In
both cases the atomic requirement for a transaction MUST be met. The
PL message header exposes ability to mark a start of transaction and
end of transaction using flags. These flags can be used to derive a
classical transactional two phase commit[ACID paper ref here].
3.3.2 FE Protocol Object
The FE Protocol Object is a logical entity in each FE that is used to
control the ForCES protocol. It is defined in the same fashion as
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LFBs. The FE Protocol Object can be manipulated using the standard
Config/Query messages. The FE Protocol Object Type ID is assigned
the value 0x1. The FE Protocol Instance ID is assigned the value
0x1. There must always be one and only one instance of the FE
Protocol Object in an FE. The values of the attributes in the FE
Protocol Object have pre-defined default values that are specified
here. Unless explicit changes are made to these values using Config
messages from the CE, these default values MUST be used for the
operation of the protocol.
The FE Protocol Object consists of the following elements:
FE Protocol events that can be subscribed/unsubscribed:
FE heartbeat
FE TML events (TBD)
FE Protocol capabilities:
Supported ForCES protocol version(s) by the FE
Supported ForCES FE model(s) by the FE
Some TML capability description(s)
FE Protocol attributes:
current version of the ForCES protocol
current version of the FE model
Association Expiry Timer
Heartbeat Interval
Primary CE
FE failover and restart policy
The FE Object (referred to as "FE attributes" in the model draft)
should not be confused with the FE Protocol Object. The FE Object
contains attributes relative to the FE itself, and not to the
operation of the ForCES protocol between the CE and the FE. Such
attributes can be FEState (refer to model draft), vendor, etc. The
FE Object Type ID is assigned the value 0x2. The FE Protocol
Instance ID is assigned the value 0x1. There must always be one and
only one instance of the FE Object in an FE.
The FE Object consists of the following elements
FE Events:
FEStatusChange (FE Up/Down/Active/Inactive/Failover)
FE DoS alert
FE capability change
FE attributes:
FE Behavior Exp. Timer
HA Mode
3.3.3 Scaling by Concurrency
It is desirable that the PL layer is not the bottleneck when larger
bandwidth pipes become available. To pick a mythical example in
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todays terms, if a 100Gbps pipe was made available and there is
sufficient work then the PL layer should take advantage and use all
of the 100Gbps pipe. Two semantics are allowed to achieve this. The
first one is batching and the second one is a command window.
Batching is ability to send multiple commands (such as config) in one
PDU. The size of the batch will be affected by amongst other things
the path MTU. The commands may be part of the same transaction or
unrelated transactions which are independent of each other. Command
windowing allows for pipelining of independent transactions which do
not affect each other. Each independent transaction could be one or
more batches.
3.3.3.1 Batching
TBD
3.3.3.2 Command Pipelining
TBD
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Internet-Draft ForCES June 20044. TML Requirements
The requirements below are expected to be delivered by the TML. This
text does not define how such mechanisms are delivered. As an
example they could be defined to be delivered via hardware or
inter-TML protocol level schemes.
Each TML must describe how it contributes to achieving the listed
ForCES requirements. If for any reason a TML does not provide a
service listed below a justification needs to be provided.
1. Reliability
As defined by RFC 3654, section 6 #6.
2. Security
TML provides security services to the ForCES PL. TML layer
should support following security services and describe how they
are achieved.
* Endpoint authentication of FE and CE.
* Message Authentication
* Confidentiality service
3. Congestion Control
The congestion control scheme used needs to be defined.
Additionally, under what circumstances is notification sent to
the PL to notify it of congestion.
4. Uni/multi/broadcast addressing/delivery if any
If theres any mapping between PL and TML level Uni/Multi/
Broadcast addressing it needs to be defined.
5. Timeliness
Editorial Note: Does the TML allow for obsoleting msgs? If yes,
it needs to say how.
6. HA decisions
It is expected that availability of transport links is the TMLs
responsibility. However, on config basis, the PL layer may wish
to participate in link failover schemes and therefore the TML
must provide this capability.
Please refer to the HA Section Section 8 for details.
7. Encapsulations used.
Different types of TMLs will encapsulate the PL messages on
different types of headers. The TML needs to specify the
encapsulation used.
8. Prioritization
It is expected that the TML will be able to handle up to 8
priority levels needed by the PL layer and will provide
preferential treatment.
TML needs to define how this is achieved.
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Internet-Draft ForCES June 20044.1 TML Parameterization
It is expected that it should be possible to use a configuration
reference point, such as the FEM or the CEM, to configure the TML.
Some of the parameters may include:
o PL ID
o Connection Type and associated data. For example if a TML uses
IP/TCP/UDP then parameters such as TCP and UDP ports, IP addresses
need to be configured.
o number of transport connections
o Connection Capability, such as bandwidth, etc.
o Allowed/Supported Connection QoS policy (or Congestion Control
Policy)
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Internet-Draft ForCES June 20045. Common Header
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|version| rsvd | Message Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Common Header
The message is 32 bit aligned.
Version (4 bit):
Version with a 2 bit major and 2 bit minor.
rsvd (4 bit):
Unused at this point. A receiver should not interpret this
field.
Command (8 bits):
Commands are defined in Section 6.
Source ID (32 bit):
Dest ID (32 bit):
* Above are 32 bit IDs which recognize the termination point.
Ideas discussed so far are desire to recognize if ID belongs
to FE or CE by inspection. Suggestions for achieving this
involves partitioning of the ID allocation. Another
alternative maybe to use flags to indicate direction (this
avoids partition).
* IDs will allow multi/broad/unicast
* Addressing
a. As ForCES may run between multiple CEs and FEs and over
different protocols such as IPv4 and IPv6, or directly
over Ethernet or other switching-fabric interconnects, it
is necessary to create an addressing scheme for ForCES
entities. Mappings to the underlying TML-level
addressing can then be defined as appropriate.
b. Fundamentally, unique IDs are assigned to CEs and FEs. A
split address space is used to distinguish FEs from CEs.
Even though we can assume that in a large NE there are
typically two or more orders of magnitude more FEs than
CEs, the address space is split uniformly for simplicity.
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c. Special IDs are reserved for FE broadcast, CE broadcast,
and NE broadcast.
d. Subgroups of FEs belonging, for instance, to the same
VPN, may be assigned a multicast ID. Likewise, subgroups
of CEs that act, for instance, in a back-up mode may be
assigned a multicast ID. These FEs and CE multicast IDs
are chosen in a distinct portion of the ID address space.
Such a multicast ID may comprise FEs, CEs, or a mix of
both.
e. As a result, the address space allows up to 2^30 (over a
billion) CEs and the same amount of FEs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|TS | sub-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: ForCES ID Format
f. The ForCES ID is 32 bits. The 2 most significant bits
called Type Switch (TS) are used to split the ID space as
follows:
A. TS Corresponding ID range Assignment
B. -- ---------------------- ----------
C. 0b00 0x00000000 to 0x3FFFFFFF FE IDs (2^30)
D. 0b01 0x40000000 to 0x7FFFFFFF CE IDs (2^30)
E. 0b10 0x80000000 to 0xBFFFFFFF reserved
F. 0b11 0xC0000000 to 0xFFFFFFEF multicast IDs
(2^30 - 16)
G. 0b11 0xFFFFFFF0 to 0xFFFFFFFC reserved
H. 0b11 0xFFFFFFFD all CEs broadcast
I. 0b11 0xFFFFFFFE all FEs broadcast
J. 0b11 0xFFFFFFFF all FEs and CEs
(NE) broadcast
g. It is desirable to address multicast and/or broadcast
messages to some LFB instances of a given class. For
instance, assume FEs FEa and FEb:
- FEa has LFBs LFBaX1 and LFBaX2 of class X
- similarly, FEb has two LFBs LFBbX1 and LFBbX2 of
class X.
A broadcast message should be addressable to only LFBs
LFBaX1 and LFBbX1 (this can be the case for instance if
these two LFBs belong to the same VPN). To achieve this,
a VPN ID (3 octets OUI and 4 octets VPN Index) as defined
in RFC 2685 should be used within the ForCES message body
as a TLV.
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As an alternative, a particular multicast ID MAY be
associated to a given VPN ID through some configuration
means. Messages delivered to such a multicast ID MUST
only be applied to LFBs belonging to that VPN ID.
Sequence (32 bits)
Unique to a PDU. [Discussion: There may be impact on the effect
of subsequence numbers].
length (16 bits):
length of header + the rest of the message in DWORDS (4 byte
increments).
Flags(32 bits):
Identified so far:
* ACK indicator(2 bit)
The description for using the two bits is:
'NoACK' (00) | 'SuccessACK'(01) | 'UnsuccessACK'(10) |
'ACKAll' (11)
*
unknown/undecided.
* Throttle flag?
* batch (2 bits)
* Atomicity (1 or 2 bits)
Editorial Note: There are several open issues, listed below, in the
header which still need to be settled:
1. Parallelization of PL Windowing/subsequence
Someone to look into ISCSI
2. events and replies and relation to peer to peer
vs master slave
3. We need to discuss whether some of the Flags
such as those for Atomicity, Batching are needed
in the common header or only belong to the
Config message.
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Internet-Draft ForCES June 20046. Protocol Messages6.1 Association Messages
The ForCES Association messages are used to establish and teardown
associations between FEs and CEs.
6.1.1 Association Setup Message
This message is sent by the FE to the CE to setup a ForCES
association between them. This message could also be used by CEs to
join a ForCES NE, however CE-to-CE communication is not covered by
this protocol.
Message transfer direction:
FE to CE
Message Header:
The Message Type in the header is set MessageType= 'Association
Setup'. The ACK flag in the header is ignored, because the setup
message will always expect to get a response from the message
receiver (CE) whether the setup is successful or not. The Src ID
(FE ID) may be set to O in the header which means that the FE
would like the CE to assign a FE ID for the FE in the setup
response message.
Message body:
The setup message body consists of one optional TLV, the format of
which is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = HBI | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Heartbeat Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8
Type (16 bits):
Currently only one Type defined, HBI-heart beat interval.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
Heartbeat Interval (32 bits):
This indicates the current HB interval on the FE in milliseconds.
A default value for this will be defined.
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Editorial Note: Whether HBI belongs to the setup is still under
discussion.
Editorial Note: In certain situations (such as use of multicast
IDs), it might not be possible to make use of the
procedure described above for the FE to
dynamically obtain an ID from the CE. Such
situations need to be identified.
6.1.2 Association Setup Response Message
This message is sent by the CE to the FE in response to the Setup
message. It indicates to the FE whether the setup is successful or
not, i.e. whether an association is established.
Message transfer direction:
CE to FE
Message Header:
The Message Type in the header is set MessageType= 'Setup
Response'. The ACK flag in the header is always ignored, because
the setup response message will never expect to get any more
response from the message receiver (FE). The Dst ID in the
header will be set to some FE ID value assigned by the CE if the
FE had requested that in the setup message (by SrcID = 0).
Message body:
The setup response message body consists of one TLV, the format
of which is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = Result | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9
Type (16 bits):
Currently only one Type i.e. Setup Result is required. Other
TLVs are optional.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
Result (16 bits):
This indicates whether the setup msg was successful or whether
the FE request was rejected by the CE.
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Internet-Draft ForCES June 20046.1.3 Association Teardown Message
This message can be sent by the FE or CE to any ForCES element to end
its ForCES association with that element.
Message transfer direction:
CE to FE, or FE to CE (or CE to CE)
Message Header:
The Message Type in the header is set MessageType= "Asso.
Teardown"(TBD?). The ACK flag in the header is always ignored,
because the teardown message will never expect to get any
response from the message receiver.
Message body:
The association teardown message body consists of one TLV, the
format of which is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = T.reason | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10
Type (16 bits):
Currently only one Type defined - Teardown Reason.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
T.reason (32 bits):
This indicates the reason why the association is being
terminated.
6.2 Query and Response Messages
Editorial Note: If the approach of using an FE Protocol & FE Object
is fully adopted and no other reason for having FE
TLVs is identified, then no distinction will be
further made in the TLV types between FE* and LFB*.
As a result, the Type ID and Instance ID in the TLV
will also be used to identify the FE Protocol
Object, with specific values as mentioned in Section3.3.2
The ForCES query and response messages are used for one ForCES
element (CE or FE) to query other ForCES element(s) for various kinds
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of information. Current version of ForCES protocol limits the use of
the messages only for CE to query information of FE. The information
to be queried in FE can be categorized into two types:
1) FE (coarse layer) information
This type of information is about the property of an FE, taking the
FE as a whole, e.g., the total available memory space in the FE. To
query this type of information, we should take the whole FE as the
addressing destination. Information of this type includes:
o Intra-FE topology
o Inter-FE topology, that is, LFB topology
o FE capabilities
o FE attributes
o FE statistics
Another way to recognize FE coarse layer property is to define two
objects, the 'FE Protocol Object' and the 'FE Object' at this coarse
layer. See Section 3.3.2 for more details.
2) LFB information
This type of information is about property of an LFB inside an FE,
e.g., routing rules of a Forwarder LFB in an FE. To query this type
of information, we should take the LFB as the addressing destination.
Information of this type include:
o LFB capabilities
o LFB attributes
o LFB statistics
6.2.1 Query Message
As usual, a query message is composed of a common header and a
message body that consists of one or more TLV data format. Detailed
description of the message is as below.
Message transfer direction:
Current version limits the query message transfer direction only
from CE to FE.
Message Header:
The Message Type in the header is set to MessageType= 'Query'.
The ACK flag in the header SHOULD be set 'ACKAll', meaning a full
response for a query message is always expected. If the ACK flag
is set other values, the meaning of the flag will then be
ignored, and a full response will still be returned by message
receiver.
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Instance ID for 'FE Protocol Object' and 'FE
Object', and others for 'FE LFB Object'.
2. Under discussion is, do we need to support
multiple objects addressing at the LFB Type
and LFB Instance layer? One simple way to
support multiple LFB types or instances is
to use TLVs to identify the group of Type
IDs and Instance IDs, rather than only one
Type and Instance ID. A range of Instance
IDs may also be supported in this way.
Query Entry:
This is a TLV that describes the entry to be queried, as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Description of the Query Entry ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12
Type:
[Under discussion and TBD]
Editorial Note: There is a debate on how the Type here can be
used. One possible use for the Type is to
specify the encoding type for the TLV value.
The possible encoding types are that like XML,
binary ID based TLV coding, etc, therefore, the
possible value for the Type may be
'XMLEncoding', 'ID-BasedBinaryEncoding', etc.
The Cons say that it may be impractical to
directly use XML encoding in the protocol
format, leaving no encoding type other than
ID-based binary encoding to be specified, hence
no need to specify encoding type. Another
possible use of the Type is to number the
entries, by which a more flexible response based
on the number may become be achieved.
Description of the Query Entry:
This field presents the detailed description about the entry to
be queried. The encoding of the description is based on the
ForCES FE model if the entry is defined by FE model, or based on
vendor specifications if the entry is defined by vendors. Note
that the encoding is responsible for the 32 bits alignment of the
description field. Usually, the description should include
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information about the name (or the name ID) of the entry to be
queried. Occasionally, it may also include some more
information, like some conditions that the queried entry is
required to meet. For instance, consider a case in which a CE is
going to query a Forwarder LFB in an FE for its current routing
table information. In this case, CE may be interested in knowing
(querying) all routing rules in the table, CE may also be
interested in only knowing (querying) a few routing rules that
meet some specific conditions, e.g., routing rules whose source
IP address should match '210.33.X.X'. In the former case, only
the name of the LFB attribute (as 'routing table') should be told
in the query entry description, while in the latter case, the
matching conditions should also be told in the description.
Taking another policer LFB as one more example, the policer LFB
may have attribute like the provisions (rules) for the policer,
therefore, in the query entry TLV, we may set the queied entry
name as the 'Provision'. To only set the name of the attribute
as 'Provision' will dump all provision items in the LFB; while to
set the attribute name and followed by some conditions will dump
the provision items that meet the conditions. The index of the
provision items can also be as the conditions, e.g., to set the
conditions as 'the index of the provision items should range from
11 to 15', then will return query result that only include the
provision items ranging from 11 to 15.
6.2.2 Query Response Message
When receiving a query message, the receiver should process the
message and come up with a query result. The receiver sends the
query result by use of the Query Response Message back to the query
message sender. The query result can be the information being
queried if the query operation is successful, or can also be error
codes if the query operation fails, indicating the reasons for the
failure.
A query response message is also composed of a common header and a
message body consists of one or more TLVs describing the query
result. Detailed description of the message is as below.
Message transfer direction:
Current version limits the query response message transfer
direction only from FE to CE.
Message Header:
The Message Type in the header is set to MessageType=
'QueryResponse'. The ACK flag in the header SHOULD be set
'NoACK', meaning no further response for a query response message
is expected. If the ACK flag is set other values, the meaning of
the flag will then be ignored. The Sequence Number in the header
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Response to Query Entry:
This is a TLV that describes the response to the queried entry,
as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Description of Response to Query Entry ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15
Type:
[Under discussion and TBD]
Description of Response to Query Entry:
This field presents the detailed description about the query
result of an entry. The encoding of the description is based on
the ForCES FE model if the entry is defined by FE model, or based
on vendor specifications if the entry is defined by vendors.
Note that the encoding is responsible for the 32 bits alignment
of the description field. When the query is successful, the
response result will include the information being queried. When
the query is failed, the response result will usually include the
information about the reason for the failure.
6.3 Configuration Messages
Editorial Note: If the approach of using an FE Protocol & FE Object
is fully adopted and no other reason for having FE
TLVs is identified, then no distinction will be
further made in the TLV types between FE* and LFB*.
As a result, the Type ID and Instance ID in the TLV
will also be used to identify the FE Protocol
Object, with specific values as mentioned in Section3.3.2
The ForCES Configuration messages are used by the CEs to configure
the FEs in a ForCES NE and report the results back to the CE.
6.3.1 Config Message
This message is sent by the CE to the FE to configure FE or LFB
attributes. This message is also used by the CE to subscribe/
unsubscribe to FE, LFB events.
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For any of the FE attribute Types, the Type, and Instance ID
fields are not present in this TLV.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
Flags (16 bits):
These can be used to indicate Atomicity, Batching, etc.
Type ID (16 bits):
This field uniquely recognizes the LFB type.
Instance ID (16 bits):
This field uniquely identifies the LFB instance.
Config Data (variable length):
This will carry LFB specific data (single or Array LFB specific
entries). The config data might itself be of the form of a TLV.
Event Type (16 bits):
For SUBSCRIBE, UNSUBSCRIBE Events Type TLVs, an Event Type field
will define the Events of interest. Examples of Event Type
include, All Events, FE Events, LFB Events, Packets, Packet
Mirroring.
6.3.2 Config Response Message
This message is sent by the FE to the CE in response to the Config
message. It indicates whether the Config was successful or not on
the FE and also gives a detailed response regarding the configuration
result of each attribute.
Message transfer direction:
FE to CE
Message Header:
The Message Type in the header is set MessageType= 'Config
Response'. The ACK flag in the header is always ignored, because
the config response message will never expect to get any more
response from the message receiver (CE).
Message body:
The Config response message body consists of one or more TLVs,
the format of a single TLV is as follows:
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Editorial Note: If the approach of using an FE Protocol & FE Object
is fully adopted and no other reason for having FE
TLVs is identified, then no distinction will be
further made in the TLV types between FE* and LFB*.
As a result, the Type ID and Instance ID in the TLV
will also be used to identify the FE Protocol
Object, with specific values as mentioned in Section3.3.2
The Event Notification Message is used for one ForCES element to
asynchronously notify one or more other ForCES elements in the same
ForCES NE on just happened events in it. The Event Notification
Response Message is used for the receiver of the Event Notification
Message to acknowledge the reception of the event notification.
Events in current ForCES protocol can be categorized into following
three types:
o Events happened in CE
o Events happened in FE at the FE coarse layer (in FE protocol
object and FE object)
o Events happened in LFB inside an FE
Events can also be categorized into two classes according to whether
they need subscription or not. An event in one ForCES element that
needs to be subscribed will send notifications to other ForCES
elements only when the other elements have subscribed to the element
for the event notification. How to subscribe/unsubscribe for an
event is described in the Configure Message in Section 6.3. An event
that needs not to be subscribed will always send notifications to
other ForCES elements when the event happens. An event definition
made by ForCES FE model or by vendors will state if the event needs
subscription or not.
Editorial Note: There is an argument that it is preferable to have
all events subscribable.
6.4.1 Event Notification Message
As usual, an Event Notification Message is composed of a common
header and a message body that consists of one or more TLV data
format. Detailed description of the message is as below.
Message Transfer Direction:
FE to CE, or CE to FE
Message Header:
The Message Type in the message header is set to
MessageType = 'EventNotification'. The ACK flag in the header can
be set as: ACK flag ='NoACK'|'SuccessAck'|'UnsuccessACK'|'ACKAll'.
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Event:
This is a TLV that describes the event to be notified, as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Description of Event ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20
Type:
[TBD]
Description of Event:
This field will make a detailed description of the happened event.
The encoding of the description is based on the ForCES FE model if
the event is defined by FE model, or based on vendor
specifications if the event is defined by vendors. Note that the
encoding is responsible for the 32 bits alignment of the
description field.The description will usually include the name
(or the name ID) of the event. It may also include some other
information like parameters that are related to the happened
event.
6.4.2 Event Notification Response Message
After sending out an Event Notification Message, the sender may be
interested in ensuring that the message has been received by
receivers, especially when the sender thinks the event notification
is vital for system management. An Event Notification Response
Message is used for this purpose. The ACK flag in the Event
Notification Message header are used to signal if such acknowledge is
requested or not by the sender.
Detailed description of the message is as below:
Message Transfer Direction:
From FE to CE or from CE to FE, just inverse to the direction of
the Event Notification Message that it responses.
Message Header:
The Message Type in the header is set MessageType=
'EventNotificationResponse'. The ACK flag in the header SHOULD be
set 'NoACK', meaning no further response for the message is
expected. If the ACK flag is set other values, the meaning of the
flag will then be ignored. The Sequence Number in the header
SHOULD keep the same as that of the message to be responded, so
that the event notificatin message sender can keep track of the
responses.
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This contains a TLV that describe the response result as below:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type='ResponseResult' | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result | Reason | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21
Result:
This describes the reception result of the event notification
message as below:
Result Value Meaning
'Success' The event has been successfully received.
'Unsuccess' The event has not been successfully received.
Reason, Code:
This describes the reason and possible error code when the message
is not successfully received. Note that only the failure at the
protocol layer rather than the transport layer can be allocated
here, that is, if even the header part of the message to be
responded can not be correctly received, the response to the
message will not be able to be generated by the receiver.
Editorial Note: There is a debate on whether the Event
Notification Response Message is necessary or
not. The pro for it is some event notification
senders may be interested in knowing if receivers
have had success/unsuccess receptions of the
events or not. An alternative to generate such
response is for the protocol to define a
universal ACK message so that it can act as
responses for any types of messages as well as
the event notification messages, when the message
senders are interested in knowing whether the
messages have been successfully received or not
(different from the responses for the message
processing results).
6.5 Packet Redirect Message
Packet redirect message is used to transfer data packets between CE
and FE. Usually these data packets are IP packets, though they may
sometimes associated with some metadata generated by other LFBs in
the model, or they may occasionally be other protocol packets, which
usually happen when CE and FE are jointly implementing some
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high-touch operations. Packets redirected from FE to CE are the data
packets that come from forwarding plane, and usually are the data
packets that need high-touch operations in CE. Packets redirected
from CE to FE are the data packets that are generated by CE and are
decided by CE to put into forwarding plane in FE.
By properly configuring related LFBs in FE, a packet can also be
mirrored to CE instead of purely redirected to CE, i.e., the packet
is duplicated and one is redirected to CE and the other continues its
way in the LFB topology.
Editorial Note: There are also discussions on how LFBs in FE model
that are related to packet redirect operations
should be defined. Although it is out of the scope
of forces protocol, how to define the LFBs affect
the Packet Redirect Message described here. Because
currently it is still in progress in FE model on how
to define such LFBs, we try to post some thoughts on
this here for discussion. They will be removed
later along with the progress of the FE model work.
Thought 1: To define LFBs called 'RedirectSink' and
'RedirectTap' for packet redirect.
An LFB in FE called 'RedirectSink' is responsible to
collect data packets that need to be redirected to
CE. From the perspective of the FE LFB topology,
the 'RedirectSink' LFB is an LFB with only one input
port and without any output port, and the input port
can then be connected to any other LFB in FE model
by means of a datapath in the forwarding plane.
From the perspective of the ForCES protocol layer,
the 'RedirectSink' LFB will generate the Packet
Redirect Messages when it receives data packets from
forwarding plane.
An LFB in FE called 'RedirectTap' is responsible to
receive data packets that are redirected from CE.
From the perspective of the FE LFB topology, the
'RedirectTap' LFB is an LFB with only one output
port and without any input port, and the output port
can then be connected to any other LFB in FE model
by means of a datapath in the forwarding plane.
From the perspective of ForCES protocol layer, the
'RedirectTap' LFB can receive the Packet Redirect
Messages from CE, and un-encapsulate the data
packets from the message and put them to datapaths
in the forwarding plane. Actually the 'RecirectTap'
LFB acts more like a transcoder that transfers the
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ForCES protocol messages to normal data packets in
IP forwarding plane. As a result, if we need to
have redirected packets connected to some LFB (say a
Scheduler) in FE model, we only need to connect the
'RedirectTap LFB to the Scheduler LFB directly via a
datapath as follows:
+-----------------+ +-----------+
| RedirectTap LFB |------>| |
+-----------------+ | |
| Scheduler |
From other LFB ---->| LFB |
| |
+-----------+
Figure 23
By use of several 'RedirectSink' LFBs and several
'RedirectTap' LFBs that connect to several different
datapaths in FE forwarding plane, multiple packet
redirect paths between CE and FE can be constructed.
Thought 2: There might be another way a packet could be
redirected: directly by a forwarding path, e.g., by
FPGA/ASIC/NP microcode. In such a case we do not
need to put in a lot of smartness. Probably a link
layer or even network level header is enough. The
receiver demuxes it only based on some protocol type
in the link layer or network transport layer. The
pros for this appraoch is it may provide a fast and
cost-effective path for packet redirect. The cons
for this is it may more or less confuses the Fp
reference point definition in ForCES framework.
We describe the Packet Redirect Message data format in details as
follows:
Message Direction:
CE to FE or FE to CE
Message Header:
The Message Type in the header is set to MessageType=
'PacketRedirect'. The ACK flags in the header SHOULD be set
'NoACK', meaning no response is expected by this message. If the
ACK flag is set other values, the meanings will be ignored.
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Message Body:
Consists of one or more TLVs, with every TLV having the following
data format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type='RedirectData' | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type ID | Instance ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Redirected Data #1 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Redirected Data #2 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Redirected Data #N ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 24
Type ID:
There are only two possible LFB types here, the 'RedirectSink' LFB
or the 'RedirectTap' LFB. If the message is from FE to CE, the
LFB type should be 'RedirectSink'. If the message is from CE to
FE, the LFB type should be 'RedirectTap'.
Instance ID:
Instance ID for the 'RedirectSink' LFB or 'RedirectTap' LFB.
Redirected Data:
This is a TLV describing one packet of data to be directed via the
specified LFB above. The order of the data number is also the
order the data packet arrives the redirector LFB, that is, the
Redirected Data #1 should arrive earlier than the Redirected Data
#2 in this redirector LFB. The TLV format is as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Description of Redirected Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 25
Type:
[TBD]
Description of Redirected Data:
This field will make a detailed description of the data to be
redirected as well as the data itself. The encoding of the
description is based on the ForCES FE model if the redirector LFB
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is defined by FE model, or based on vendor specifications if the
redirector LFB is defined by vendors. The description will
usually include the name (or the name ID) of the redirected packet
data (such as 'IPv4 Packet', 'IPv6 Packet'), and the packet data
itself. It may also include some metadata (metadata name (or name
ID) and its value)associated with the redirected data packet.
6.6 State Maintenance Messages
The State Maintenance Messages are used by the CE to change state
related information on the FE.
Editorial Note: As work progresses in defining the FE model, it may
happen that the messages defined here (State
Maintenance messages) become redundant. For
instance, FE activation/deactivation may be
performed by configuring the FE State attribute in
the FE Object. Such inconsistencies will be
resolved
6.6.1 State Maintenance Message
This message is sent by the CE to change the state of the FE, e.g.
to Activate/Deactivate the FE, shutdown the FE, etc.
Message transfer direction:
CE to FE
Message Header:
The Message Type in the header is set MessageType= 'State
Maintenance'. The ACK flag in the header is can be used by the
CE to turn off any response from the FE. The default behavior is
to turn on the ACK to get the state maintenance response from the
FE.
Message body:
The state maintenance message body consists of one or more TLVs,
the format of a single TLV is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type= FE De/Activate,Shutdown | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 26
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Type (16 bits):
These can be FE Activate, FE Deactivate, Shutdown FE. Activating
an FE means asking it to forward packets, Deactivate means the FE
stops forwarding packets. The default state of the FE is
deactivated till it explicitly activated by the CE.
Editorial Note: These Types may be extended to include LFB
Activate/Deactivate as well. However this is
still being discussed.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
FE State object (variable):
This is an TLV which can be defined and extended to represent FE
specific state information. It will contain information such as
the HA Mode, Primary CE ID, etc for the FE.
6.6.2 State Maintenance Response Message
This message is sent by the FE to the CE in response to the state m.
message. It indicates whether the state m. was successful or not on
the FE.
Message transfer direction:
FE to CE
Message Header:
The Message Type in the header is set MessageType= 'state m.
Response'. The ACK flag in the header is always ignored, because
the state m. response message will never expect to get any more
response from the message receiver (CE).
Message body:
The state maintenance response message body consists of one or
more TLVs, the format of a single TLV is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type= S.M.Result | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 27
Type (16 bits):
Same as that for state maintenance message.
Length (16 bits):
Length of the TLV including the T and L fields, in bytes.
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Overall Result (16 bits):
This indicates the overall result of the state maintenance
message, whether it was successful or it failed.
6.7 Heartbeat Message
The Heartbeat (HB) Message is used for one ForCES element (FE or CE)
to asynchronously notify one or more other ForCES elements in the
same ForCES NE on its liveness.
A Heartbeat Message is sent by a ForCES element periodically. The
time interval to send the message is set by the Association Setup
Message described in Section 6.1.1. A little different from other
protocol messages, a Heartbeat messge is only composed of a common
header, withe the message body left empty. Detailed description of
the message is as below.
Message Transfer Direction:
FE to CE, or CE to FE
Message Header:
The Message Type in the message header is set to MessageType =
'Heartbeat'. The ACK flag in the header SHOULD be set to
'NoACK', meaning no response from receiver(s) is expected by the
message sender. Other values of the ACK flag will always be
ignored by the message receiver.
Message Body:
The message body is empty for the Heartbeat Message, so as to
grasp more efficiency for message transportation and processing.
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Internet-Draft ForCES June 20047. Protocol Scenarios7.1 Association Setup state
The associations among CEs and FEs are initiated via Association
setup message from the FE. If a setup request is granted by the CE,
a successful setup response message is sent to the FE. If CEs and
FEs are operating in an insecure environment then the security
association have to be established between them before any
association messages can be exchanged. The TML will take care of
establishing any security associations.
This is followed by capability query, topology query. When the FE is
ready to start forwarding data traffic, it sends a FE UP Event
message to the CE. The CE responds with a FE ACTIVATE State
Maintenance message to ask the FE to go active and start forwarding
data traffic. At this point the association establishment is
complete. These sequences of messages are illustrated in the Figure
below.
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Note that the sequence of messages shown in the figure serve only as
examples and the messages exchange sequences could be different from
what is shown in the figure. Also, note that the protocol scenarios
described in this section do not include all the different message
exchanges which would take place during failover. That is described
in the HA section 8.
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Internet-Draft ForCES June 20048. High Availability Support
Editorial Note: This section currently focuses only on CE-CE
redundancy. We need to further discuss the FE-FE
view. We also need to discuss Multiple Primary CEs.
The ForCES protocol provides mechanisms for CE redundancy and
failover, in order to support High Availability. There can be
multiple redundant CEs and FEs in a ForCES NE. However, at any time
there can only be one Primary CE controlling the FEs and there can be
multiple secondary CEs. The FE and the CE PL are aware of the
primary and secondary CEs. This information (primary, secondary CEs)
is configured in the FE, CE PLs during pre-association by FEM, CEM
respectively. Only the primary CE sends Control messages to the FEs.
The FE may send its event reports, redirection packets to only the
Primary CE (Report Primary Mode) or it may send these to both primary
and secondary CEs (Report All Mode). (The latter helps with keeping
state between CEs synchronized, although it does not guarantee
synchronization.) This behavior or HA Modes are configured during
Association setup phase but can be changed by the CE anytime during
protocol operation. A CE-to-CE synchronization protocol will be
needed in most cases to support fast failover, however this will not
be defined by the ForCES protocol.
During a communication failure between the FE and CE (which is caused
due to CE or link reasons, i.e. not FE related), the TML on the FE
will trigger the FE PL regarding this failure. The FE PL will send a
message (Event Report) to the Secondary CEs to indicate this failure
or the CE PL will detect this and one of the Secondary CEs takes over
as the primary CE for the FE. An explicit message (State Maintenance
Move command) from the primary CE, can also be used to change the
Primary CE for an FE during normal protocol operation. In order to
support fast failover, the FE will establish association (setup msg)
as well as complete the capability exchange with the Primary as well
as all the Secondary CEs (in all scenarios/modes).
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Internet-Draft ForCES June 20049. Security Considerations
ForCES architecture identified several [Reference Arch] levels of
security. ForCES PL uses security services provided by the ForCES
TML layer. TML layer provides security services such as endpoint
authentication service, message authentication service and
confidentiality service. Endpoint authentication service is invoked
at the time of pre-association connection establishment phase and
message authentication is performed whenever FE or CE receives a
packet from its peer.
Following are the general security mechanism that needs to be in
place for ForCES PL layer.
o Security mechanism are session controlled that is once the
security is turned ON depending upon the chosen security level (No
Security, Authentication only, Confidentiality), it will be in
effect for the entire duration of the session.
o Operator should configure the same security policies for both
primary and backup FE's and CE's (if available). This will ensure
uniform operations, and to avoid unnecessary complexity in policy
configuration.
o ForCES PL endpoints SHOULD pre-established connections with both
primary and backup CE's. This will reduce the security messages
and enable rapid switchover operations for HA.
9.1 No Security
When No security is chosen for ForCES protocol communication, both
endpoint authentication and message authentication service needs be
performed by ForCES PL layer. Both these mechanism are weak and does
not involve cryptographic operation. Operator can choose "No
security" level when the ForCES protocol endpoints are within an
single box.
In order to have interoperable and uniform implementation across
various security levels, each CE and FE endpoint MUST implement this
level. The operations that are being performed for "No security"
level is required even if lower TML security services are being used.
9.1.1 Endpoint Authentication
Each CE and FE PL layer maintain set of associations list as part of
configuration. This is done via CEM and FEM interfaces. FE MUST
connect to only those CE's that are configured via FEM similarly CE
should accept the connection and establish associations for the FE's
which are configured via CEM. CE should validate the FE identifier
before accepting the connection during the pre-association phase.
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Internet-Draft ForCES June 20049.1.2 Message authentication
When CE or FE generates initiates a message, the receiving endpoint
MUST validate the initiator of the message by checking the common
header CE or FE identifiers. This will ensure proper protocol
functioning. We recommend this extra step processing even if the
underlying TLM layer security services.
9.2 ForCES PL and TML security service
This section is applicable if operator wishes to use the TML security
services. ForCES TML layer MUST support one or more security service
such as endpoint authentication service, message authentication
service, confidentiality service as part of TML security layer
functions. It is the responsibility of the operator to select
appropriate security service and configure security policies
accordingly. The details of such configuration is outside the scope
of ForCES PL and is depending upon the type of transport protocol,
nature of connection.
All these configurations should be done prior to starting the CE and
FE.
When certificates-based authentication is being used at TML layer,
the certificate can use ForCES specific naming structure as
certificate names and accordingly the security policies can be
configured at CE and FE.
9.2.1 Endpoint authentication service
When TML security services are enabled. ForCES TML layer performs
endpoint authentication. Security association is established between
CE and FE and is transparent to the ForCES PL layer.
We recommend that FE after establishing the connection with the
primary CE, should establish the security association with the backup
CE (if available). During the switchover operation CE's security
state associated with each SA's are not transferred. SA between
primary CE and FE and backup CE and FE are treated as two separate
SA's.
9.2.2 Message authentication service
This is TML specific operation and is transparent to ForCES PL
layer[TML document].
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Internet-Draft ForCES June 2004Appendix C. Implementation NotesC.1 TML considerations
Having separated the PL from the TML layer, it became clear that the
TML layer needed to understand the desires of the PL layer to service
it. Example: How does the TML layer map prioritization or
reliability needs of a PL message? To see the challenge involved,
assume that all of the FE TML, FE PL, CE TML and CE PL are
implemented by different authors probably belonging to different
organizations. Three implementation alternatives were discussed.
As an example, consider a TML which defines that PL messages needing
reliability get sent over a TCP connection; then TML-PL interfaces
are:
o PL to call a special API: example send_reliable(msg) which is
translated by the TML to mean send via TCP.
o PL to call a generic API: example send(msg) with explicit msg
flags turned to say "reliability needed" and the TML translates
this to mean send via TCP.
o PL sends the Forces Messages such a message is inferred to mean
send via TCP by the TML.
in #1 and #2 the msg includes a ForCES msg with metadata flags which
are consumed by the TML layer.
#3 is a technique that will be referred as inference-by-TML
technique. It simplifies the standardization effort since both #1
and #2 will require standardization of an API. Two ideas discussed
for TML inference of PL messages are:
1. Looking at the flags in the header.
2. Looking at the message type.
#1 and #2 can still be used if a single organization implements both
(PL and TML) layers. It is also reasonable that one organization
implements the TML and provides an abstraction to another
organization to implement a PL layer on.
C.1.1 PL Flag inference by TML
1. Reliability
This could be "signalled" from the PL to the TML via the ACK
flag. The message type as well could be used to indicate this.
2. No reliability
Could be signalled via missing ACK flag. The message type as
well could be used to indicate this.
3. Priorities
A remapping to be defined via the FEM or the CEM interface
depending on the number of TML priorities available.
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4. Addressing
This is TML specific. For example a TML that is capable of
multicast transport may map a multicast PL ID to a multicast
transport address.
5. Event notifications
The TML must be able to send to the PL notifications.
1. The TML should be able to send Transport level congestion
notifications to the PL.
2. Link events for HA purposes if configuration requires it
3. Events that will trigger PL layer events from the TML.
As an example, an HA event at the TML layer like a failure of
CE detected at TML on the FE may belong to this. In this
case, a PL event msg will be triggered and sent to CE.
4. Events that are intrinsic to the same CE or FE a TML is
located. These will not trigger any PL msg, instead, they
just act as notification to PL core (FE object). The
congestion event generated at the transmission source side
may belong to this, because it usually only needs to tell the
upper PL at the same side rather than the opposite side that
congestion has happened along the path. E.g., a congestion
event at CE TML layer only need to tell CE PL of this, rather
than the opposite FE via a PL msg.
C.1.2 Message type inference to Mapping at the TML
In this case one would define the desires of the different message
types and what they expect from the TML. For example:
1. Association Setup, Teardown, Config, Query the PL will expect the
following services from TML: Reliable delivery and highest
prioritization.
2. Packet Redirect, HB Message Types, and Event Reports the PL will
require the following services from TML: Medium Prioritization,
and notifications when excessive losses are reached.
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